Spark ignition internal combustion engines such as are used in automobiles have traditionally employed mechanical and/or electronic distributors to route high voltage energy from an ignition coil to the engine spark plugs. More recently, distributorless ignition systems have been employed in which a separate ignition coil is provided for every one or two spark plugs. In some cases, the coils are generally located above the spark plug(s). In other cases, the coils are integrated together into a common housing or assembly for installation above the spark plugs as a single unit.
FIG. 1 illustrates another manner in which conventional engines provide high voltage energy to a spark plug. More particularly, FIG. 1 illustrates what is referred to in the art as a coil-on-plug (COP) assembly 10 that includes a conventional ignition wire 12. This ignition wire 12 (also shown in FIG. 2) may be characterized as a spring of sorts that has a voltage source end 14 that, when in use, is electrically interconnected with a coil (not shown) disposed within a coil portion 13 of an insulative boot 20 of the COP assembly 10. In addition, this ignition wire 12 has a plug end 16 that, when in use, is electrically interconnected to a spark plug 18.
It has been found that deployment of the ignition wire 12 in the COP assembly 10 is problematic. For instance, due to the conventional design of the ignition wire 12, during use the plug end 16 of the same tends to melt and at least generally adhere the ignition wire 12 to the spark plug 18. This results in increased labor when it comes time to replace the spark plug 18. Moreover, even if the plug end 16 of the ignition wire 12 does not meltingly adhere to the spark plug 18, the amount of force utilized to dissociate the spark plug 18 from the plug end 16 of the ignition wire 12 generally causes the spring-shaped ignition wire 12 to stretch without recoiling back to its original length. This stretching of the ignition wire 12 may undesirably result in a portion of the ignition wire 12 extending out beyond a plug end 19 of the insulative boot 20. Once this ignition wire 12 has been stretched, it generally quite difficult to return the ignition wire 12 to its original length. Accordingly, the simple task of replacing the spark plug 18 associated with this COP assembly 10 may undesirably be accompanied by replacement of the ignition wire 12 or even the entire COP assembly 10. This adds undesired expense and time to the task of replacing the spark plug 18.
In addition to the above-described problems associated with the ignition wire 12, the conventional type of ignition wire 12 also has been shown to provide a resistance of no less than about 6 ohms. Accordingly, the performance of the engine is at least generally hindered with the deployment of this ignition wire 12 in the COP assembly 10.